DescentBB

trying to get to sleep, i got up and decided to read about Rebreathers instead, i found this online:

http://www.isracast.com/tech_news/310505_tech.htm wrote:LIKE A FISH â??
REVOLUTIONARY UNDERWATER BREATHING SYSTEM
An Israeli Inventor has developed a breathing apparatus that will allow breathing underwater without the assistance of compressed air tanks. This new invention will use the relatively small amounts of air that already exist in water to supply oxygen to both scuba divers and submarines. The invention has already captured the interest of most major diving manufacturers as well as the Israeli Navy.

the article mentions the inspiration being those little underwater breathing things they used in StarWars "The Phantom Menace". Which is the start of the same train of thought that eventually got me outof bed to read about rebreathers

This system is basically a rebreather - with the oxygen tank replaced with a centrifuge that harvests disolved air from the water (much like a fish's gills).

The diving forum that linked to it was phoopooing the idea saying it'l never work. But i like it.

Well, look at it this way: Water is H2O. The goal is oxygen. We know how to separate hydrogen from oxygen. All these things do is use that process to split off the oxygen, then use it for the diver. The DISADVANTAGE is the amount of energy required to perform this function--you'll have to carry a bulky battery pack around with you when you dive, and you can only stay under as long as your battery lasts.

the Germans were working on this during WWII....I can't imagine how it found it's way into the hands of an Isreali

Stryker wrote:Well, look at it this way: Water is H2O. The goal is oxygen. We know how to separate hydrogen from oxygen. All these things do is use that process to split off the oxygen, then use it for the diver. The DISADVANTAGE is the amount of energy required to perform this function--you'll have to carry a bulky battery pack around with you when you dive, and you can only stay under as long as your battery lasts.

nono, what you describe is ELECTROLOSIS. Fish don't use electrolosis to extract disolved air from water. This device - like fish gills - extracts DISOLVED air from water, which takes a great deal less energy than electrolosis.

but is not dissolved air useless...I'm assuming "dissolved air" would be air devoid of oxygen

you can dissolve gasses in liquids much like you can disolve solids in liquids.

both CO2 and Oxygen can be dissolved in water. This is how fish can get the Oxygen they need and underwater plants can get CO2 they need. Under the sea it's just like on land - animals breath in Oxygen and breathe out CO2 - photosynthesising plants breathe in CO2 and breathe out Oxygen.

The word "Dissolved" doesn't at all mean "devoid of oxygen".
When i say "Dissolved Air" i mean all the gasses in air - all dissolved into the water. It may have made more sense if i just said Oxygen, but i didn't want to imply that Oxygen was the only gas dissolved in water - i'm sure all the gasses in air are dissolved in water to some extent.

(apologies, i was spelling Dissolved with only one S)

Reminds me of the joke whose punchline is, "because air is free"

btw, I think those bubble things in aquariums cause air/oxygen to be dissolved in water. This is what the fish gills extract.

I can see clearly now...thanks

N/M

CUDA we've had rebreathers for decades.
http://en.wikipedia.org/wiki/Rebreather

edit: lol.

will_kill wrote:but is not dissolved air useless...I'm assuming "dissolved air" would be air devoid of oxygen

That would prevent the notion of "fish".

As a SCUBA diver myself, I would be very interested in such a system if it ever became commercially available. I wonder if your bottom time would be limited in some way as it is now due to nitrogen absorption into the blood stream. Interesting.

Dedman wrote:As a SCUBA diver myself, I would be very interested in such a system if it ever became commercially available. I wonder if your bottom time would be limited in some way as it is now due to nitrogen absorption into the blood stream. Interesting.

Isn't that because you have a limited oxygen supply? Having that device would solve that because you wouldn't run out of oxygen, but the longer you stay down the longer it takes to decompress on the way back up IIRC. Least thats what they say on TV.

Silicon film can form a watertight surface that allows oxygen to pass thru. The membrane has to be sliced 1/2000th of an inch thick and laminated together with two layers to prevent leaks. It forms a permeable membrane, capable of transmitting oxygen thru its surface. For a human being, a cage the size of an eight foot cube, or 260 square feet of film would be required to sustain a human underwater. With special care and compression, one could imagine creating a "radiator" with the same surface area much smaller and more compact, allowing for a "water lung" that a scuba diver could easily hold on his back, exchanging oxygen in the water for oxygen in his "water lung".

interesting lobber, got any more info on that?

Hrmm... very interesting concept. But is the "air" dissolved in water of the same concentration of constituents as the air above the surface?

You can get nitrogen narcoses if you stay under water too long and you don't decompress properly.

A problem I see is that you need pressurized air to breath. The reason you can't just take a long tube with you and dive 100 feet is that your diaphram isn't strong enough to suck the air in at 3 or how many atmospheres. With an air tank, the air is pressurized for the depth you're at, so you can just take normal breaths through the regulator.

Yeah... other thing is there isn't very much air in water. You'd either need some kind of machinery or to breathe like hell to get enough...

P.S. guess - there may be far more atmospheric oxygen than is necessary for humans anyway...

Krom wrote:Isn't that because you have a limited oxygen supply? Having that device would solve that because you wouldn't run out of oxygen, but the longer you stay down the longer it takes to decompress on the way back up IIRC. Least thats what they say on TV.

Yes and no. Theoretically, if you have an unlimited supply you could stay down indefinately I suppose. While great for commercial divers, that doesn't do a sport diver much good. If you want to do multiple dives in one day or have to fly the next day, you have to be very mindfull of the total time you were at any given depth. It's all about the management of nitrogen absorption. I was just wondering how this little gizmo would affect that.

will_kill wrote:but is not dissolved air useless...I'm assuming "dissolved air" would be air devoid of oxygen

Heh, I am SOOOO glad you're not God